1. Field Of The Invention
The present invention relates to apparatus for the continuous conversion of thin web material into corrugated board. More specifically, the present invention relates to improvements in stripper fingers which strip a web from the surface of one corrugating nip roll and confine the web closely against the surface of the other corrugating roll about a portion of the circumference thereof.
2. Description Of The Prior Art
In the art of converting thin material webs such as paper to corrugated board, the length of a traveling web is pressure formed into a continuum of corrugated undulations. This forming occurs in the meshing nip between two cylindrical roller elements having fluted surfaces. The corrugation flutes of the roller surfaces extend longitudinally parallel with the roller axes and transversely of the web length. Flutes respective to each of the two roller elements mesh together like gear teeth. Consequently, a corrugation forming pressure is exerted on the web by drawing it between the meshing roll flutes.
Subsequent to forming, adhesive is applied to the crests of the web flutes and a liner or facing web is pressed thereagainst to fabricate what is known to the industry as single faced board.
Upon emerging from the corrugated forming nip, the web must be positively stripped from the fluted surface of one roller and maintained in contiguous contact with the surface of the other roller. This contiguous contact must be maintained against the natural tendency of the corrugated web to spring away from the roller surface.
To accomplish these two functions of stripping and contact maintenance, the art has utilized a series of thin crescent shaped elements called stripper fingers. Each forming nip has a plurality of stripper fingers equally spaced along the nip length approximately 2 to 4 inches apart. For each stripper finger, a thin slot is cut around the circumference of one nip roll so that the tips of the stripper fingers may project under the meshing region and form a continuous surface to guide the web away from the slotted roll and onto the other roll.
This guide surface continues around an arcuate portion of the other roll with minimal clearance between the guide surface and the roll surface flute crests to permit the web thickness to be carried therebetween. The guide surface arc continues from the corrugation forming nip to a pressure nip whereat the liner web is applied.
Since an integral strip of web is of finite length, a subsequent strip must be threaded through the machine when a previous strip is exhausted. The most convenient and expeditious technique of such threading is to lap join the leading edge of the subsequent strip with the trailing edge of the previous strip. However, this technique results in a short length of double thickness web passing between the stripper finger guide edges and the other corrugating roll surface. Since the stripper fingers are usually of light gauge, soft metal sheet stock, they will yield to accommodate the double thickness but may permanently deform in the process. Such deformation then creates additional operational problems arising from the consequence that the following single thickness of web will spring away from the respective corrugating roll surface.